In aircraft engines, it is a good practice to have protection against a missing or misinstalled tank filler cap. In the case of oil tanks, such protection is to prevent oil loss in situations where the oil filler cap is forgotten, misinstalled or if it comes off due to a failure during engine operation. Such a protection may allow completion of a flight mission by preserving oil in the tank and hence ensuring that engine oil consumption is maintained below the maximal oil consumption rate in a situation where the cap is missing.